Process for the manufacture of benzene hexachloride



PROCESS FOR THE MANUFACTURE OF EENZIEIIE HEXACHLURIDE Ford R.Lowderrnillr, Gwynedd Valley, and Everett A. Bruce, Pauli, Pa, assiguorsto The Pennsylvania Salt Manufacturing Company, Philadelphia, Pa, acorporation of Pennsylvania No Drawing. Application November 4, 1952,Serial No. 318,753

8 Claims. (Cl. 26l)643) This invention relates to processes for theremoval and recovery of organic liquors adhering to benzenehexachloricle solids.

Benzene hexachloride solids are important commercially in that the gammaisomer has insecticidal properties not possessed by the other isomers.The principal commercial processes for the manufacture of a gammabenzene hexachloride provide for the photochemical chlorination ofbenzene which produces the gamma isomer along with the alpha, beta,delta, epsilon, and other isomers of benzene hexachloride. The gammaisomer usually comprises 12 to 15% of the total benzene hexachlorideproduced in the chlorination process. Many processes have been devisedto upgrade this gamma isomer concentrationthe ultimate being theproduction of a substantially pure gamma material.

One of these processes for the production of a gammaenriched benzenehexachloride is that of La Lande et al. as set forth in U. S. Patent2,569,677. In this process benzene is chlorinated to the extent that aslurry is formed consisting of a liquid phase comprising benzene anddissolved benzene hexachloride isomers and a solid phase of undissolvedbenzene hexachloride isomers. The chlorination slurry upon filtrationyields a benzene solution of benzene hexachloride high in gamma isomercontent and a filter cake containing solid benzene hexachloride isomersconsisting substantially of the alpha and beta isomers wet with thebenzene solution of the dissolved isomers.

Another process that yields benzene heXachloride solids with adheringliquors is described in copending application Serial Number 136,408,filed December 31, 1949, now abandoned. In that process there isobtained a filter cake high in gamma isomer but containing some of theother isomers as part of the solids and also containing an adheringmother liquor consisting of either benzene or petroleum ether withdissolved benzene hexachloride isomers.

The usual practice in the industry heretofore, where a separation ismade of benzene hexachloride solids from solvent solutions thereof, hasbeen to wash the deliquored benzene heXachloride solids with portions ofsolvent free of dissolved benzene heXachloride isomers and usually at alow temperature in order to suppress solubility of benzene hexachloridewith resulting partial displacement of the liquors adhering to thesolids. The displacement of mother liquor is an important considerationin processes for upgrading gamma benzene hexachloride. Moreover,recovery of the mother liquor is important for economical processoperation.

Repeated displacements of the residual liquor adhering to the benzenehexachloride solids are necessary when the mother liquor is veryvaluable and its dilution by the wash liquor does not adversely affectthe economy of the operation. Thus, three or more displacement washesare considered normal in many industrial filtration operations. However,extensive dilution of liquors high in gamma isomer concentration isusually undesirable in tates Patent most benzene hexachloride processes.Concurrently with the effect of dilution by the application of repeatedsolvent washes, the subsequent disposition of the deliquored benzenehexachloride solids must be considered in devising a practical benzenehexachloride solids washing and recovery process. In processes whereinthe deliquored solids are further utilized in gamma benzene hexachloridemanufacture, the problem of recovery of the washing solvent is not asimportant as its dilution effect on the mother liquor. In the processeswherein the benzene hexachloride solids are discarded or diverted toprocesses unrelated to gamma benzene hexachloride manufacture, theproblem of the recovery of the displacement solvents or wash solvents isof considerable importance. In such cases the cost of the recoveryoperation of the solvent is compared with the value of the recoveredsolvent in determining the feasibility of the recovery operation.

We have now found a simple process for the removal and recovery oforganic liquors adhering to benzene hexachloride solids which consistsof washing the benzene hexachloride solids with an aqueous solution ofan organic wetting agent at a temperature at which both the adheringsolvent liquor and the wash water remain in the liquid state. Thispractice of the invention makes unnecessary the extensive application ofdisplacement liquors with resultant dilution of the mother liquor wherethe wash liquor is the same as the mother liquor. In the preferredoperation of our invention the benzene hexachloride solids, after adeliquoring operation, are first washed with a solvent to displacemother liquor and thereafter washed with an aqueous solution of anorganic wetting agent, at a temperature at which both the organic liquorand the wash water remain liquid, to recover residual mother liquor andwash liquor.

This new invention is particularly applicable to the process of La Landeet al., supra. In this process the chlorination slurry is deliquored toproduce benzene hexach-loricle solids consisting principally of thealpha and beta isomers and containing adhering benzene mother liquorwherein the gamma isomer content of the total dissolved solids isapproximately 25 to 50%. Several washings of the alpha-beta solids withcold benzene leaves the residual solids wet with benzene to the extentof 10 to 13% of the total weight of the solids and in additionconsiderable amounts of the valuable gamma isomer are retained in thecake. This residual benzene and gamma benzene hexachloride is lost withthe disposal or diversion of the unwanted alpha-beta cake from benzenehexachloride processes. Application of an aqueous solution of an organicwetting agent to the alpha-beta solids removes the residual benzene andgamma benzene hexachloride to the extent that their concentration in thefinal alpha and beta solids is less than 1% benzene and practically nogamma benzene hexachloride. After filtration, the benzene solution ofbenzene hexachloride is separated from the Water, preferably bydecantation and is combined with the gamma-enriched mother liquor of thechlorination process. Surprisingly, no dilution of the gamma isomercontent has occurred through the washing and recovery process so that itcan be combined with the mother liquor from the chlorination process.The separated wash water containing the wetting agent is reused insubsequent washings.

This invention is also of particular value in another I preferably freeof dissolved benzene hexachlorides.

tion of an organic Wetting agent. This washing operation removes theminor proportion of the adulterating benzene hexachloride isomers andimpurities in solution in the mother liquor and produces a benzenehexachloride solid of enhanced gamma isomer content.

In one form of our invention, which employs a solvent wash prior to theaqueous wash, the solvent washing liquid may be of the same identity asthe mother liquor. This is of particular value in that another componentis not added to the existing system. Advantageously, this Washingliquor, of the same identity as the mother liquor, is It is particularlyadvantageous when the washing solvent is also immiscible with water sothat separation of the washing solvents and organic liquors from thesubsequent aqueous wetting agent wash is readily eifected byStratification. Organic liquors as used herein and throughout thisapplication means organic solvents with or without dissolved benzenehexachloride solids therein, and may refer to either residual motherliquor or residual solvent wash liquor.

When using the term washing throughout this application, it is meant theprocesses wherein liquids are applied to solids to displace adheringliquors, followed by physical processes to separate the applied liquidsfrom the solids. The wash liquor may be applied as a stream or as aspray to the benzene hexachloride solids and it is intended to includerepulping processes wherein the benzene hexachloride solids are stirredwith the Wash solvent prior to deliquoring. The deliquoring operationmay occur through the application of gravitational forces or throughphysical forces such as centrifugal force.

Of the many wetting agents useful in the practice of this invention,those from the classes designated as alkylated polyether alcohol and thesodium salts of sulphuric acid esters of saturated fatty alcohols havingmore than eight carbon atoms are particularly advantageous. Specificmembers of the above classes, which are particularly desirable inpracticing our recovery processes, are Triton X 155 from the first classand sodium lauryl sulfate from the fatty alcohol sulfate class. Thislatter surface active agent is sold under the trade name of Duponol WA.

Other members of the fatty alcohol sulfate class which have been founduseful are known under trade names as Maprofix and Wetanol. Anotheralkylated aryl polyether alcohol which is useful in practicing thisinvention is a compound wherein the alkyl group is an isooctyl radical,the aryl group is a phenol, and where the polyether alcohol groupcontains 12 to 16 condensed ethoxy groups. This is sold under the tradename of Triton X 100.

Other wetting agents found useful in practicing our invention are asfollows: Nacconollong-chain alkyl ben zene sulfonate, Igepon AP andIgepon Tsulfonated amides, Aerosol OT-dioctyl ester of sodiumsulfosuccinic acid, Aerosol MA-dihexyl ester of sodium sulfosuccinicacid, Armeensfatty acid amines, Emulgorpolyhydric alcohol ether fattyacid condensate, Glycox, Kalavan, Polyethylene glyco-400 monostearate,Polyethylene glyco- 400 monooleate, naphthalene 2,7 disulphonic acid,Glycox 2005, sodium oleate, and calcium phenol sulfonatee The aqueoussolutions of wetting agents wherein the concentration of the surfaceactive agent is as low as 0.005% by weight have been found useful inpracticing our inventiotn. Advantageously, the lower concentration limitof the surface active agent is 0.01% by weight. The maximumconcentration of surface active agents useful in our process isdetermined by the solubility limitations of the surface active agents inwater and by economic considerations. Thus, only solutions are useful inour process, and usually dilute solutions for the sake of economy.

The surface active agent is applied to the benzene hexachloride solidsas an aqueous solution. Moreover, the temperature of the aqueoussolution must be regulated so that the adhering organic liquor remainsin the liquid phase throughout the washing cycle. If the aqueoussolution of the surface active agent is too high in temperature, theadhering organic liquor will flash, thus depositing its dissolved solidsin the benzene hexachloride solids. This flashing would defeat thepurification purposes of the washing operations. It has been foundparticularly advantageous in practicing our invention to adjust thetemperature of the aqueous solution of the wetting agent so that itremains within the range of 30 to 70 C. when applied to the benzenehexachloride solids.

The separation of the organic liquors from the aqueous solution of theorganic wetting agent may be effected in any convenient manner. In thecase where the organic liquor is immiscible with water, the separationprocess may be effected by stratification such as decantation or by theapplication of centrifugal forces. In those cases where the adheringorganic liquors are miscible in the aqueous solution of the organicwetting agent, the separation may be effected by distillation and/orextraction processes.

The following examples are illustrative of the process of the invention:

Example I in a benzene mother liquor saturated with respect to allisomers of benzene hexachloride was filtered on a 40 gallon Nutsche typefilter. The filter cake was then washed twice with 3 gallon portions ofpure benzene. The filter cake after the benzene wash contained 12.9%benzene and 1.1% of gamma benzene hexachloride. The filtration andbenzene washing operations Were carried out at about F. to F.

The cake was then washed with 28 gallons of an aqueous solution ofsodium lauryl sulfate (Duponol WA) in which the concentration of thesodium lauryl sulfate was 0.055% by weight. The temperature of the washwater was about 75 F. As filtrate 23 gallons of Wetting agent solutionwere recovered in the aqueous layer while 27 pounds of organic materialwere recovered in the organic layer. The recovered organic layercontained 62.6% benzene and 14% of the gamma isomer of benzenehexachloride, the remainder being the other isomers of benzenehexachloride. After water washing the cake on the filter contained 5.9%benzene and no detectable gamma isomer of benzene hexachloride.

In contrast to this, a slurry consisting of 200 gm. of the alpha andbeta isomers of benzene hexachloride and 200 gm. of mother liquor Wassubjected to filtration. The mother liquor in the slurry contained about50% benzene and was saturated with respect to the alpha and betaisomers. The gamma isomer constituted about 36% of the benzenehexachloride content of the mother liquor.

After filtration tap water was then applied to the surface of the cakeand vacuum applied to the filter flask. The wash Water failed topenetrate the cake.

Example II 100 gm. of benzene was mixed with 200 gm. of benzenehexachloride which contained 88% of the gamma isomer. The mixture washeated to dissolve all the benzene hexachloride and then cooled toprecipitate a crop of benzene hexachloride crystals. This cooled mixturewas then filtered on aBuchner filter.

The wet cake resulting from this filtration was washed on the filterwith 47 grams of benzene. The cake was then washed with 189 gm. of watercontaining about 0.08 gm. of Duponol WA. As a result of thiswater-Washing operation about 5 .8 gm. of benzene-benzene hexachloridesolution was removed from the cake. The gamma isomer content of the cakeprior to the water washing operation was about 98.8%. The gamma isomercontent of the cake after the water washing operation was about 99.5%.

Example III A mixture consisting of 300 gm. of dry alpha beta isomers ofBHC and 300 gm. of benzene mother liquor was placed in a Buchner vacuumfilter. The mother liquor contained about 50% benzene and 50% dissolvedbenzene hexachloride solids. The benzene hexachlorides in solutionanalyzed about 36% gamma isomer while the mother liquor was saturatedwith respect to the alpha and beta isomers of benzene hexachloride.Vacuum was applied to the filter and 188 gm. of mother liquor wasrecovered as filtrate. The moist filter cake was then repulpcd with 600gm. of water containing 1 /2 gm. of Triton X 155 wetting agent and thenrefiltered on the Buchner funnel. After filtration the combined organiclayer and water layer were placed in a separatory funnel forstratification.

Example IV To illustrate operation at the higher temperatures, a slurrywas made up consisting of 27 pounds benzene plus 38% pounds of the alphaand beta isomers of benzene hexachloride plus 1 pound of filter aid.This was filtered on a Nutsche type vacuum filter. The cake formed onthe filter was washed once with 6%. pounds of benzene. The benzenerecovered in the filtrate at this point was about 18 pounds leavingabout 15 pounds of benzene (about 45% of the total charge) remaining asadherent organic liquor in the filter cake. A wash consisting of 41%pounds of hot water containing about 0.04% wt. percent of Duponol wasintroduced to the benzene hexachloridc solids on the filter. The waterwas applied at about 75 C., cooled immediately on contact to below 70C., and cooled to 55 C. during the operation. The wash water penetratedthe cake easily and displaced from the cake organic liquor containing 10lb. oz. of benzene. A trap filled with charcoal in the vacuum line fromthe filter adsorbed an additional 7 oz. of benzene. The total benzeneremoved from the cake by application of the hot aqueous wetting agentsolution was thus 11 lb. 6 oz.

Operating as described in the above examples, the process can be appliedto removal and recovery of other organic solvents commonly used inprocesses for upgrading the gamma isomer content of benzenehexachloride. Such solvents include toluene, Xylenes, carbontetrachloride, chloroform, petroleum hydrocarbons, such as the petroleumethers and higher aliphatic hydrocarbons, cyclohexane and othercycloaliphatics, in general, solvents such as those listed in column 3of U. S. Patent 2,438,900 and in U. S. Patent 2,502,258. It is alsoapplicable to remove water soluble organic solvents from benzenehexachloride solids, for example recovering methanol, ethanol,isopropanol or other alcohol mother liquor (containing some dissolvedgamma isomer) from the alpha and beta isomers and other benzenehexachlorides remaining as solids after extraction of gamma isomer froma total benzene chlorination product, or removal of acetic acid from analpha-beta cake or other benzene hexachloride solids.

It will be obvious to one skilled in the art that each of the aboveexamples may be operated employing any of the wetting agents listedabove or equivalent surfactants known in the art.

We claim:

1. In a process for the recovery of a water immiscible organic liquoradhering to benzene hexachloride solids, the steps comprising washingthe benzene hexachloride solids containing adhering water immiscibleorganic liquor with an aqueous solution of an organic wetting agent at atemperature at which both the water immiscible organic liquor and thewash water remain liquid, thereafter withdrawing a mixture of waterimmiscible organic liquor and the said aqueous solution of the organicwetting agent from contact with said solids and separating the saidorganic liquor from the said aqueous solution.

2. In a process for the recovery of water immiscible mother liquor andsolvent wash liquor adhering to benzene heXachloride solids, the stepscomprising washing the benzene hexachloride solids containing adheringwater immiscible mother liquor with an organic liquid of the sameidentity as the mother liquor, thereafter washing the said benzenehexachloride solids with an aqueous solution of an organic wetting agentat a temperature at which both the water immiscible organic liquor andthe wash water remain liquid, withdrawing a mixture of the said organicliquor and the said aqueous solution of the organic Wetting agent fromcontact with said solids and separating the said organic liquor from thesaid aqueous solution.

3. In a process for the recovery of water immiscible organic liquorcontaining gamma-enriched benzene hexachloride adhering to benzenehexachloride solids consisting substantially of the alpha and betaisomers, the steps comprising washing the benzene hexachloride solidsconsisting substantially of the alpha and beta isomers and containingadhering water immiscible organic liquor with dissolved gamma isomertherein with an aqueous solution of an organic wetting agent at atemperature at which both the water immiscible organic liquid and theaqueous solution remain liquid, thereafter withdrawing a mixture of thesaid organic liquor and the aqueous solution of the said wetting agentfrom contact with said solids, and separating the recovered waterimmiscible organic liquor from the said aqueous solution of the organicwetting agent.

4. The process of claim 2 in which the organic wash solvent is benzenewhich is free of dissolved benzene hexachloride and Washing of thebenzene hexachloride solids with an aqueous solution of a wetting agentis performed at a temperature of 30 to 70 C.

5. In a process for enhancing the gamma isomer content of a benzenehexachloride filter cake consisting of a major proportion of gammaisomer and a minor proportion of other benzene hexachloride isomers andimpurities and containing gamma enriched benzene hexachloride waterimmiscible liquor adhering to the said filter cake, the steps comprisingwashing the said benzene hexachloride filter cake with an aqueoussolution of an organic wetting agent at a temperature at which both thewater immiscible organic liquor and the said aqueous wash solutionremain liquid, thereafter withdrawing a mixture of water immiscibleorganic liquor and aqueous wash solution of the said wetting agent fromcontact with said benzene hexachloride filter cake and separating thesaid organic liquor from the said aqueous wash solution.

6. In a process for the recovery of Water immiscible organic liquoradhering to benzene hexachloride solids the steps comprising washing thebenzene hexachloride solids containing adhering water immiscible organicliquor with an aqueous solution of an organic wetting agent selectcdfrom the class consisting of alkylated polyether alcohols, sodium saltsof sulfuric acid esters of saturated fatty alcohols having in excess of8 carbon atoms, long chain alkyl benzene sulfonates, sulfonated amides,alkyl esters of sodium sulfosuccinic acid, fatty acid amines, andpolyhydric alcohol ether fatty acid condensates at a temperature atwhich both the water immiscible organic liquor and the said aqueous washsolution remain liquid, thereafter withdrawing a mixture of the saidorganic liquod and the said aqueous wash solution from contact with saidsolids, and separating the said organic liquor from the said aqueouswash solution.

7. The process of claim 6 in which the organic wetting agent is analkylated polyether alcohol.

8. The process of claim 6 in which the organic Wetting agent is thesodium salt of sulfuric acid esters of saturated fatty alcohols havingin excess of 8 carbon atoms.

Rowland et a1 July 4, 1950 La Lande et al Oct. 2, 1951

1. IN A PROCESS FOR THE RECOVERY OF A WATER IMMISCIBLE ORGANIC LIQUORADHERING TO BENZENE HEXACHLORIDE THE STEPS COMPRISING WASHING IMMISCIBLEORGANIC LIQUOR SOLIDS CONTAINING SOLUTION OF AN ORGANIC WETTING AGENT ATWITH AN AQUEOUS SOLUTION OF AN ORGANIC WETTING AGENT AT A TEMPERATURE ATWHICH BOTH THE WATER IMMISCIBLE ORGANIC LIQUOR AND THE WASH WATER REMAINLIQUID, THEREAFTER WITHDRAWING A MIXTURE OF WATER IMMISCIBLE ORGANICLIQUOR AND THE SAID AQUEOUS SOLUTION OF THE ORGANIC WETTING AGENT FROMCONTACT WITH SAID SOLIDS AND SEPARATING THE SAID ORGANIC LIQUOR FROM THESAID AQUEOUS SOLUTION.